[LARTC] SMP in regards to routing/filtering

[LARTC] SMP in regards to routing/filtering

[Phil Doroff]

Hey, quick (stupid) question..

	Is the routing/filtering code in the linux kernel able to take much
advantage of SMP?  I'm building a router that I'd like to be able to handle
at least 450mbit/sec (64bit 66mhtz PCI slots of course) and be able to apply
QoS (basic prio queues) and htb/etc. traffic shaping to.

Just wondering if it's worth grabbing an extra processor for the box, or if
it will largely go unused.

Thanks!

Phil Doroff
Five Elements, Inc.
phil21@five-elements.com
Phone:(763)595-9479 ICQ: 25285313

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Re: [LARTC] SMP in regards to routing/filtering

[bert hubert]

On Fri, Aug 30, 2002 at 10:11:46PM -0500, Phil Doroff wrote:
> Hey, quick (stupid) question..
> 
> 	Is the routing/filtering code in the linux kernel able to take much
> advantage of SMP?  I'm building a router that I'd like to be able to handle
> at least 450mbit/sec (64bit 66mhtz PCI slots of course) and be able to apply
> QoS (basic prio queues) and htb/etc. traffic shaping to.

Under some circumstances, a second CPU can be very useful. It depends on
what you are doing, but the Linux networking core is completely able to
paralelly use processors. 

You may need to do some work to give each network adaptor a dedicated CPU
and you will also want to have multiple PCI busses.

> Just wondering if it's worth grabbing an extra processor for the box, or if
> it will largely go unused.

It will see use but if you mess things up, it will not help. So make sure
that you search on 'irq affinity' and the utility of multiple PCI busses.
Perhaps a 64-bit 66MHz bus is fast enough to get by with one.

Regards,

bert hubert

-- 
http://www.PowerDNS.com          Versatile DNS Software & Services
http://www.tk                              the dot in .tk
http://lartc.org           Linux Advanced Routing & Traffic Control HOWTO
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Re: [LARTC] SMP in regards to routing/filtering

[David Boreham]

> > Just wondering if it's worth grabbing an extra processor for the box, or
if
> > it will largely go unused.

It is also possible that two processors will be _slower_ than one,
due to contention. So it will be worthwhile to test with one CPU
disabled (UP kernel) just to see what happens.



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